Search

This article presents the Automatic Speaker Recognition System (ASR System), which successfully resolves problems such as identification within an open set of speakers and the verification of speakers in difficult recording conditions similar to telephone transmission conditions. The article provides complete information on the architecture of the various internal processing modules of the ASR System. The speaker recognition system proposed in the article, has been compared very closely to other competing systems, achieving improved speaker identification and verification results, on known certified voice dataset. The ASR System owes this to the dual use of genetic algorithms both in the feature selection process and in the optimization of the system's internal parameters. This was also influenced by the proprietary feature generation and corresponding classification process using Gaussian mixture models. This allowed the development of a system that makes an important contribution to the current state of the art in speaker recognition systems for telephone transmission applications with known speech coding standards. [ABSTRACT FROM AUTHOR]

The Rossmann fold enzymes are involved in essential biochemical pathways such as nucleotide and amino acid metabolism. Their functioning relies on interaction with cofactors, small nucleoside-based compounds specifically recognized by a conserved βαβ motif shared by all Rossmann fold proteins. While Rossmann methyltransferases recognize only a single cofactor type, the S-adenosylmethionine, the oxidoreductases, depending on the family, bind nicotinamide (nicotinamide adenine dinucleotide, nicotinamide adenine dinucleotide phosphate) or flavin-based (flavin adenine dinucleotide) cofactors. In this study, we showed that despite its short length, the βαβ motif unambiguously defines the specificity towards the cofactor. Following this observation, we trained two complementary deep learning models for the prediction of the cofactor specificity based on the sequence and structural features of the βαβ motif. A benchmark on two independent test sets, one containing βαβ motifs bearing no resemblance to those of the training set, and the other comprising 38 experimentally confirmed cases of rational design of the cofactor specificity, revealed the nearly perfect performance of the two methods. The Rossmann-toolbox protocols can be accessed via the webserver at https://lbs.cent.uw.edu.pl/rossmann-toolbox and are available as a Python package at https://github.com/labstructbioinf/rossmann-toolbox. [ABSTRACT FROM AUTHOR]

The aim of this work was to investigate the influence of Leucidal® Liquid (abbr. Leucidal), which is recommended as a natural cosmetic ingredient of antimicrobial properties, on model membranes of keratinocytes and fibroblasts. The toxicity tests on cell lines were also performed to allow for a more detailed discussion of the results. As model membrane systems the lipid Langmuir monolayers were applied. During the investigations, the surface pressure/area measurements, penetration studies and Brewster Angle Microscopy (BAM) visualization were performed for one component and mixed lipid monolayers. It was evidenced that at the membrane – corresponding conditions, the components of Leucidal do not penetrate either model keratinocyte and fibroblast membranes or one component films composed of the major lipids of skin cell membranes. Leucidal makes these systems slightly more expanded and less stable, however this is not reflected in the changes in the film morphology. Only the ceramide systems were sensitive to the presence of Leucidal, i.e. the incorporation of Leucidal components manifested well in the decrease of the films' condensation and alterations in their morphology. The tests on cells demonstrated that Leucidal is non toxic for these types of cells at the concentrations suggested by the producer. A thorough comparison of these results with those published for bacteria model membranes enabled us to discuss them in the context of the mechanism of action of Leucidal components. It was concluded that Leucidal components are of low affinity to the skin cellular model membranes of low content of Leucidal-sensitive ceramides and are not toxic for fibroblast and keratinocyte cell lines. Moreover, the lipid composition of the membrane and its molecular organization can be important targets for Leucidal components, decisive from the point of view of the activity and selectivity of the studied composition. [Display omitted] • The components of Leucidal do not penetrate the model membranes of keratinocytes or fibroblasts. • Only the ceramide systems were sensitive to the presence of Leucidal. • Leucidal components are not toxic for fibroblast and keratinocyte cell lines. [ABSTRACT FROM AUTHOR]

• Terahertz imaging was suitable for ceramic ballistic protection armor. • Terahertz XY raster scanner with terahertz time-domain spectroscopy was used. • The transfer matrix method simulated the terahertz signals. • Interfaces and regular pattern of hexagonal alumina tiles were clearly visible. • The position and shape of puncture defects matched the reference X-ray images. We prepared an alumina-based ceramic ballistic protection armor sample consisting of hexagonal alumina tiles arranged in a honeycomb structure, glued with Kevlar®, and covered with a polyurethane-based resin. The sample was shot with four projectiles, strongly hit from the back, and locally covered with water. The terahertz complex refractive index of the materials constituting the sample was measured. A terahertz time-domain spectroscopy (THz-TDS) setup in a reflection configuration was used to raster scan the XY sample. The results in the form of time signals, top views, and cross-sections enabled an understanding the internal structure of the sample. THz-TDS was proved to be suitable for non-destructive testing of the alumina-based armors with depth-discriminant 3D imaging. Transfer matrix method (TMM) correctly simulated terahertz signals reflected from the sample, calculated the thickness of the sample layers, and help determine the type of hidden defects. [ABSTRACT FROM AUTHOR]

• Automatic defect detection in glass composites using terahertz radiation. • Time-domain spectroscopy reflective scanner with an electronically controlled optical sampling scheme. • Pre-selection of C-scans with defect-related features. • Thresholding method based on Gaussian histogram fitting. • Size and depth of inclusions and delaminations determined with high accuracy. We developed a method for automatic detection of defects in glass fibre reinforced polymer (GFRP) based on a terahertz time-domain spectroscopy (TDS) system. Two GFRP specimens with round defects of different sizes (inclusions and delaminations) were measured by means of a high-speed TDS reflective scanner with an electronically controlled optical sampling scheme. The algorithm provided a series of C-scans, which were then pre-selected to identify only those with features potentially associated with defects. A thresholding method based on Gaussian fitting of the histogram was developed. The results showed that 87 % of defects were detected for the specimen with inclusions and 100 % for the specimen with delaminations. The algorithm also provided information about the depth of defects, as each C-scan was assigned to a time slice. The results demonstrate that the TDS-based system, along with the proposed histogram-based method, can automatically detect defects in GFRP. © 2017 Elsevier Inc. All rights reserved. [ABSTRACT FROM AUTHOR]

Phenomena that occur between an insulin and four different positively charged polymers (protamine, cationic dextran, chitosan, and poliallylamine derivatives) were studied by dynamic light scattering and fluorescence measurements (using fluorescein-labeled polymers). These processes were compared to the reaction of polycations with heparin that is responsible for the neutralization of anticoagulant activity in blood stream.The nature of polycations interaction with heparin is electrostatic, while the interaction with insulin is more complicated.We observed that the presence of zinc atoms (and its complexing by nitrogen from macromolecules) is critical for insulin suspensions formation and stability. The differences between the nature of these two reactions were revealed. The highly immunogenic action of protamine present in long-acting insulin products makes it reasonable to develop similar systems based on the nonprotein polycations. [ABSTRACT FROM AUTHOR]

In this study, a high-pressure-assisted photoinduced atom transfer radical polymerization (p ≤ 250 MPa) enabled the synthesis of ultra-high-molecular-weight polymers (UHMWPs) of up to 9 350 000 and low/moderate dispersity (1.10 < Đ < 1.46) in a co-solvent system (water/DMSO), without reaction mixture deoxygenation. [ABSTRACT FROM AUTHOR]

The interaction between oppositely charged membranes and polycations causes cell aggregation, loss of membrane fluidity, and membrane degeneration and may cause an increase of its permeability. Unfortunately, the interaction is the reason why the use of polycations in medicine is severely limited. Therefore, in this paper, we share our observations related to the action of 40-kDa dextran modified using glycidyltrimethylammonium chloride, resulting in increased fibroblast cell proliferation. Using viability and proliferation tests [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, crystal violet, 3H-thymidine incorporation], we have observed that cationic dextran derivatives exert a positive impact on nonepithelial cell proliferation in vitro. This phenomenon has been noted for human and mouse fibroblasts and several other nonepithelial cell lines. However, the effect seems to be most pronounced for fibroblast cell lines. The presented studies allow to examine the impact of the polymer structure and the methods of its cationic modification on this newly observed phenomenon. The observation is unique because positively charged macromolecules usually exhibit high toxicity in all cell types in vitro. [ABSTRACT FROM AUTHOR]

We investigate the previously postulated hydrodynamic steering phenomenon, resulting from complication of molecular shapes, its magnitude and possible relevance for protein--ligand and protein--protein diffusional encounters, and the kinetics of diffusion-controlled association. We consider effects of hydrodynamic interactions in a prototypical model system consisting of a cleft enzyme and an elongated substrate, and real protein--protein complexes, that of barnase and barstar, and human growth hormone and its binding protein. The kinetics of diffusional encounters is evaluated on the basis of rigid-body Brownian dynamics simulations in which hydrodynamic interactions between molecules are modeled using the bead-shell method for detailed description of molecular surfaces, and the first-passage-time approach. We show that magnitudes of steering torques resulting from the hydrodynamic coupling of associating molecules, evaluated for the studied systems on the basis of the Stokes--Einstein type relations for arbitrarily shaped rigid bodies, are comparable with magnitudes of torques resulting from electrostatic interactions of binding partners. Surprisingly, however, unlike in the case of electrostatic torques that strongly affect the diffusional encounter, overall effects of hydrodynamic steering torques on the association kinetics, while clearly discernible in Brownian dynamics simulations, are rather minute. We explain this result as a consequence of the thermal agitation of the binding partners. Our finding is relevant for the general understanding of a wide spectrum of molecular processes in solution but there is also a more practical aspect to it if one considers the low level of shape detail of models that are usually employed to evaluate hydrodynamic interactions in particle-based Stokesian and Brownian dynamics simulations of multicomponent biomolecular systems. Results described in the current work justify, in part at least, such a low-resolution description. [ABSTRACT FROM AUTHOR]

Two cationic derivatives of γ-cyclodextrin (GCD) were synthesized by functionalization with glycidyltrimethylammonium chloride (GTMAC) and ethylenediamine (EDA). Both these derivatives (GCD-GTMAC and GCD-EDA) have been shown to interact strongly with anionic biopolymers, unfractionated heparin (UFH) and mucin, the latter showing their mucoadhesive properties. They form inclusion complexes with daidzein (DAI), an isoflavone displaying a multitude of physiological effects, much more efficiently than the unmodified GCD. It was also shown that the complexes of these GCD derivatives with DAI and Nile Red penetrate human fibroblasts and murine hippocampal neuronal cells indicating that cationic GCD derivatives can be considered as potential delivery systems for isoflavones and other poorly water soluble compounds. Moreover, it was found that DAI delivered in cationic GCD complexes decreased the level of the cellular glycosaminoglycans (GAGs) in normal fibroblasts suggesting their possible application in the control of GAGs in mucopolysaccharidoses, lysosomal storage diseases caused by pathological accumulation of GAGs in the cells. [ABSTRACT FROM AUTHOR]

We built a high-speed TDS setup with the use of electronically controlled optical sampling (ECOPS), which can measure up to 1600 terahertz pulses per second. The movement of the sample was provided by two fast-speed motorized linear stages constituting the gantry. We developed a flat-bar-based metal marker approach for the synchronization of continuous line-by-line scans. We carefully compared the performance of the terahertz reflection time-domain spectroscopy (TDS) scanner operating in a slow point-by-point and a one-hundred-times faster line-by-line imaging scheme. We analyzed images obtained for both schemes for a uniform metallic breadboard with holes, as well as a glass composite sample with defects. Although the measurement time was reduced by 100 times in terms of the line-by-line scheme, the overall performance in both schemes was almost identical in terms of the defects' sizes, shapes and locations. The results proved that the proposed ECOPS TDS system can provide uniform and extremely fast scanning without any deterioration in image quality. [ABSTRACT FROM AUTHOR]

Diallyl disulfide (DADS) and diallyl trisulfide (DATS) are garlic oil compounds exhibiting beneficial healthy properties including anticancer action. However, these compounds are sparingly water-soluble with a limited stability that may imply damage to blood vessels or cells after administration. Thus, their encapsulation in the oil-core nanocapsules based on a derivative of hyaluronic acid was investigated here as a way of protecting against oxidation and undesired interactions with blood and digestive track components. The nuclear magnetic resonance (1H NMR) technique was used to follow the oxidation processes. It was proved that the shell of the capsule acts as a barrier limiting the sulfur oxidation, enhancing the stability of C=C bonds in DADS and DATS. Moreover, it was shown that the encapsulation inhibited the lysis of the red blood cell membrane (mainly for DADS) and interactions with serum or digestive track components. Importantly, the biological functions and anticancer activity of DADS and DATS were preserved after encapsulation. Additionally, the nanocapsule formulations affected the migration of neoplastic cells—a desirable preliminary observation concerning the inhibition of migration. The proposed route of administration of these garlic extract components would enable reaching their higher concentrations in blood, longer circulation in a bloodstream, and thus, imply a better therapeutic effect. [ABSTRACT FROM AUTHOR]

• Artillery combustible cartridge case scanned with terahertz radiation. • THz rotary scanner with time domain spectroscopy in reflection configuration. • Wire polariser employed as a reference for stable time difference determination. • Case radius measured with an uncertainty of 0.04 mm. • Thickness of the case wall determined with an uncertainty of 0.03 mm. In this study, terahertz radiation was employed to determine the radius, diameter, and thickness of the nitrocellulose combustible cartridge case used for tank ammunition. The construction of the sample was outlined, and the refractive index of the case material was measured. A terahertz rotary scanner with a time-domain spectroscopy setup in reflection configuration was developed, and its performance and parameters were determined. A wire polariser was introduced as a reference to determine the stable time difference. The radius and diameter measurements of the case were based on a reference terahertz pulse reflected from its metal base. The thickness of the case was calculated based on the time difference between pulses reflected from its inner and outer surfaces. These measurements were in agreement with the reference measurements. The results prove that the developed setup and measurement methods are suitable for the non-destructive evaluation of cases and provided satisfactory performance. [ABSTRACT FROM AUTHOR]

We show the remarkable effect of using static (DC) and alternating (AC) electric fields to control the free-radical polymerization of methyl methacrylate (MMA). The magnitude and/or frequency of the applied electric field (up to 154 kV cm−1) were found to control the molecular weight, dispersity, and stereochemistry of the produced polymers. [ABSTRACT FROM AUTHOR]

The routine monitoring of direct oral anticoagulants (DOACs) may be considered in patients with renal impairment, patients who are heavily obese, or patients requiring elective surgery. Using the heparin-binding copolymer (HBC) and polybrene, we aimed to develop a solution for monitoring the anticoagulant activity of DOACs in human plasma in the interfering presence of unfractionated heparin (UFH) and enoxaparin. The thrombin time (TT) and anti-factor Xa activity were monitored in pooled plasma from healthy volunteers. In these tests, plasma with dabigatran or rivaroxaban was mixed with UFH or enoxaparin and then incubated with HBC or polybrene, respectively. HBC and polybrene neutralized heparins and enabled monitoring of anticoagulant activity of dabigatran in the TT test. Both agents allowed for accurate measurement of anti-factor Xa activity in the plasma containing rivaroxaban and heparins in the concentration range reached in patients' blood. Here, we present diagnostic tools that may improve the control of anticoagulation by eliminating the contamination of blood samples with heparins and enabling the monitoring of DOACs' activity. [ABSTRACT FROM AUTHOR]

In this paper, we propose one-step synthetic strategies for obtaining well-defined linear and star-shaped polyvinylpyrrolidone (linPVP and starPVP). The produced macromolecules and a commercial PVP K30 with linear topology were investigated as potential matrices for suppressing metronidazole (MTZ) crystallization. Interestingly, during the formation of binary mixtures (BMs) containing different polymers and MTZ, we found that linear PVPs exhibit maximum miscibility with the drug at a 50:50 weight ratio (w/w), while the star-shaped polymer mixes with MTZ even at a 30:70 w/w. To explain these observations, comprehensive studies of MTZ-PVP formulations with various contents of both components were performed using Fourier-transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction. The obtained results clearly showed that the polymer's topology plays a significant role in the type of interactions occurring between the matrix and MTZ. Additionally, we established that for MTZ-PVP 50:50 and 75:25 w/w BMs, linear polymers have the most substantial impact on inhibiting the crystallization of API. The star-shaped macromolecule turned out to be the least effective in stabilizing amorphous MTZ at these polymer concentrations. Nevertheless, long-term structural investigations of the MTZ-starPVP 30:70 w/w system (which is not achievable for linear PVPs) demonstrated its complete amorphousness for over one month. [ABSTRACT FROM AUTHOR]

The structures of the plastic crystal (PC), orientational glass (OTG), liquid (LQ) and ordinary glass (OG) phases of 1,6‐anhydro‐β‐d‐glucopyranose (levoglucosan) have been investigated using X‐ray diffraction and molecular modeling. The experimental diffraction data in the forms of static structure factors and pair distribution functions are analyzed in reciprocal and real spaces and compared with results of model‐based simulations. A new approach to modeling the structure of the disordered phases, taking into account the intermolecular scattering contribution in the form of sharp Bragg peaks, the slowly varying intensity associated with intramolecular correlations and the diffusive component resulting from structural disorder, is applied. In the case of the LQ and OG samples, reverse Monte Carlo simulations are also used. The PC and OTG phases show long‐range ordering of the hexagonal close‐packed (hcp)‐type structure up to 120 Å with random orientation of the molecules. Assuming a rigid molecular skeleton, isotropic free rotations of the molecules about their geometrical center in full and limited angular ranges are generated in theoretical models of the structure. It is demonstrated that the adoption of free rotations of the molecules leads to the best fits to experimental data for each studied phase of levoglucosan. The diffraction patterns of the LQ and OG samples show a relatively sharp first peak originating from quasi‐Bragg planes of the densely packed face‐centered cubic (fcc) type molecular arrangement. Moreover, the slowly varied intensity component of LQ and OG is practically the same as that of PC and OTG, suggesting that the intramolecular structure of these four phases does not change. Interestingly, structural correlations for the disordered LQ and OG states extend surprisingly far, up to about 50 Å. In addition, for all levoglucosan phases investigated, the paracrystalline disorder imposed on the generated models resulted in better compliance with the experimental data. [ABSTRACT FROM AUTHOR]

The nanoemulsion-based delivery systems have gained particular attention due to effective encapsulation and protection of hydrophobic active compounds. However, several features like limited stability, cellular uptake or release of payloads still need to be addressed. We investigated the uptake of the nanocapsules based on the amphiphilic derivative of hyaluronate with oleic acid cores (oil-in-water nanoemulsion) and their anticancer activity in vitro. The core-shell nanocapsules exhibiting long term stability in dispersion showed an enhanced uptake by cancer cells and effectively killed them only if composed of hyaluronate-based shells and oleic acid cores - the anionic chitosan-based shells and/or corn oil cores were used for control experiments. We concluded that the nanocapsules stabilized by the amphiphilic derivative of hyaluronic acid may serve as very stable and efficient delivery systems for oil-soluble compounds without necessity of application of low molecular weight (co)surfactants. The in vitro studies indicated anticancer activity of such delivered oleic acid and crucial role of hyaluronate shell of the nanocapsules in its efficient delivery and enzyme-triggered disintegration inside cells. Corn oil was shown as a nutrient that can serve as an inert vehicle in the studied nanoemulsion that exhibit application potential in food, dietary supplement industry and medicine. Unlabelled Image • Nanocapsules with hyaluronate-based shell and oil core are efficiently uptake intracellularly. • Oleic acid in hyaluronate-based nanocapsules shows superior anticancer activity in vitro. • Cellular hyaluronidases degrade the capsules shell releasing their oil cores. [ABSTRACT FROM AUTHOR]

The lack of the N-alpha-glucosaminidase (Naglu) is responsible for the incidence of a rare disease - mucopolysaccharidosis, type IIIB (MPS IIIB). To date, studies have been conducted based on cells derived from patients suffering from MPS or using in vivo MPS mouse models. These limitations have allowed for defining our research goal - to create and characterize the first in vitro murine cellular MPS IIIB model. In the current work we present a new, stable cell line with confirmed accumulation of glycosaminoglycans. The line stability was achieved by immortalization using a lentivirus carrying the T-antigens of SV40. The Naglu −/− cells were confirmed to produce no Naglu enzyme. To confirm the proper functioning of the in vitro MPS IIIB model, we determined the activity and expression of cystathionine γ-lyase, rhodanese and 3-mercaptopyruvate sulfurtransferase, as well as the level of low molecular-weight thiols (reduced and oxidized glutathione, cysteine and cystine). The results were referred to our earlier findings originating from the studies on the tissues of the Naglu −/− mice that were used to create the lines. The results obtained in the Naglu −/− cells were in accordance with the results found in the mouse model of MPS IIIB. It suggests that the presented murine Naglu −/− cell lines might be a convenient in vitro model of MPS IIIB. • The Naglu −/− cell lines may be an in vitro model of mucopolysaccharidosis type IIIB. • The cysteine level is elevated in the Naglu −/− cells. • The Naglu −/− cells have a weak antioxidant potential. • endo- and exogenous heparan sulfate demonstrate different biological activity. [ABSTRACT FROM AUTHOR]

Herein, we examined the effect of finite size and wettability on the structural dynamics and the molecular arrangement of the propylene carbonate derivative, (S)-(−)-4-methoxymethyl-1,3-dioxolan-2-one (assigned as s-methoxy-PC), incorporated into alumina and silica porous templates of pore diameters d = 4 nm–10 nm using Raman and broadband dielectric spectroscopy, differential scanning calorimetry, and x-ray diffraction. It was demonstrated that only subtle changes in the molecular organization and short-range order of confined s-methoxy-PC molecules were detected. Yet, a significant deviation of the structural dynamics and depression of the glass transition temperatures, Tg, was found for all confined samples with respect to the bulk material. Interestingly, these changes correlate with neither the finite size effects nor the interfacial energy but seem to vary with wettability, generally. Nevertheless, for s-methoxy-PC infiltrated into native (more hydrophilic) and modified (more hydrophobic) silica templates of the same nanochannel size (d = 4 nm), a change in the dynamics and Tg was negligible despite a significant variation in wettability. These results indicated that although wettability might be a suitable variable to predict alteration of the structural dynamics and depression of the glass transition temperature, other factors, i.e., surface roughness and the density packing, might also have a strong contribution to the observed confinement effects. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract A cationic derivative of γ-cyclodextrin (GCD) modified with propylenediamine (PDA) was synthesized. It was shown that the derivative (GCD–PDA) is mucoadhesive and resistant to the digestion with ∝-amylase indicating that it may constitute an efficient oral delivery vehicle. GCD-PDA formed an inclusion complex with berberine (BBR), an alkaloid displaying a multitude of beneficial physiological effects. The complexed BBR penetrates a lipid membrane easier than the free one. Both uncomplexed BBR and that complexed with GCD-PDA was delivered to normal (NMuMG) and cancerous (4T1) murine mammary gland cells. In the normal cells both free and complexed BBR was homogeneously dispersed in the cytoplasm and was nontoxic up to 131 μM. In the cancerous cells uncomplexed BBR was also homogeneously dispersed but it was toxic to about 25% of cells at 131 μM, while the GCD-PDA/BBR complex was preferably localized in lysosomes and its toxicity doubled at this concentration compared to that of free BBR. Moreover, free BBR and GCD-PDA/BBR showed even more efficient inhibitory effect against murine melanoma (B16-F10) cells than against 4T1 cells. [ABSTRACT FROM AUTHOR]

Abstract Lactobacillus rhamnosus GG is an environmentally and human-friendly bacteria that can be found in probiotics. However, it is incapable of forming a biofilm on metal surfaces, what limits the possibility of using it in bioelectrochemical systems (BESs) as promising and green alternatives. Hence, we propose a simple and cost-effective modification of metal surface with cationic dextran derivative (DEX-G) by using the electrostatically driven self-assembly procedure resulting in the formation of a polymeric monolayer. Modification of metal electrodes was confirmed by using infrared spectroscopy (IR) and atomic force microscopy (AFM). Synthesized metal/polycation electrodes provided a bioactive environment for L. rhamnosus GG enhancing its proliferation and formation of the biofilm as confirmed by SEM imaging. Moreover, using cyclic voltammetry (CV) and chronoamperometry measurements, it was proven that metal/polycation/ L. rhamnosus bioelectrodes are electrochemically active in the glucose-rich medium. The electrochemical activity of fabricated bioanodes allows to consider them for their potential use in the bioelectrochemical systems. Graphical abstract Image 1 Highlights • Metal surface modification method facilitating the biofilm formation is proposed. • Use of lactic acid bacteria for bioelectrochemical systems is examined. • Cationic dextran coating enhanced bacteria colonization of gold. • The electroactivity of proposed bioanodes was confirmed by cyclic voltammetry. [ABSTRACT FROM AUTHOR]

• The structural (α)-process in loratadine (LOR) is sensitive to compression. • The pressure dependence of τ JG β is weaker with respect to that of τ α. • There is a breakdown of exact isochronal α and JG β superpositioning in LOR. • Reason for that is probably the increase of order in the system due to densification. In this paper, high-pressure (HP) dielectric studies on the van der Waals active pharmaceutical ingredient (API) - loratadine (LOR) were carried out. It was found that, surprisingly, the secondary (β) relaxation, which, according to the Coupling Model (CM) predictions, was classified as a Johari-Goldstein (JG) process, separates from the structural (α)-mode with compression (although the shape of the α -peak is invariant to the thermodynamic conditions at constant τ α). Consequently, there is a breakdown of the isochronal superpositioning of α - and β - relaxation times (τ α and τ β) in this system, which is a typical behavior for the secondary process with intermolecular character. Based on these findings, two possibilities concerning the origin of the β -relaxation in LOR have been proposed: 1) it is a non-JG process (probably originating from fluctuations within cyclic rings of the API molecule), which, however, satisfies the CM predictions; or 2) it is a JG-process, which similarly to a few earlier examined H-bonded compounds (e.g., probucol and sorbitol) is characterized by a different sensitivity to compression when compared to the α -process. Moreover, it was found that the activation entropy for the β -process takes negative values, irrespective of the pressure conditions. That may be interpreted as a result of conformational variation or the loss of translational and rotational degrees of freedom, leading to increased order in API due to densification. The results presented herein give a new insight into the relationship between the structural and secondary relaxations in the close vicinity of the glass transition temperature. Furthermore, they show that HP studies are crucial in elucidating the correlation between these processes. [ABSTRACT FROM AUTHOR]

In this paper, the molecular dynamics at different thermodynamic conditions of hydrogen-bonded (H-bonded) active pharmaceutical ingredient—ticagrelor (TICA) have been investigated. Extensive high-pressure (HP) dielectric studies revealed surprising high sensitivity of the structural (α)-relaxation to compression. They also showed that unexpectedly the shape of the α-peak remains invariable at various temperature (T) and pressure (p) conditions at constant α-relaxation time. Further infrared measurements on the ordinary and pressure densified glasses of the examined compound indicated that the hydrogen-bonding pattern in TICA is unchanged by the applied experimental conditions. Such behavior was in contrast to that observed recently for ritonavir (where the organization of hydrogen bonds varied at high p) and explained the lack of changes in the width of α-dispersion with compression. Moreover, HP dielectric measurements performed in the glassy state of TICA revealed the high sensitivity of the slow secondary (β)-relaxation (Johari–Goldstein type) to pressure and fulfillment of the isochronal superpositioning of α- and JG-β-relaxation times. Additionally, it was found that the activation entropy for the β-process, estimated from the Eyring equation (a high positive value at 0.1 MPa) slightly increases with compression. We suggested that the reason for that are probably small conformational variations of TICA molecules at elevated p. [ABSTRACT FROM AUTHOR]

In this paper, efficient MMA photo O-ATRP protocols conducted inside nanoreactors varying in nanostructured interfaces are reported for the first time. We showed that the microstructure of recovered polymers could be easily tuned just by implementing a given type of nanochannel (d = 10, 19–28, 35, 160 nm). [ABSTRACT FROM AUTHOR]

In this paper, thermal properties, atomic-scale structure, and molecular dynamics (at ambient and high pressure) of native melatonin (MLT) and its partially-deuterated derivative (MLT-d2) have been investigated. Based on infrared spectroscopy, it was shown that treating MLT with D2O causes the replacement of hydrogen atoms attached to the nitrogen by deuterium. The degree of such substitution was very high (> 99%) and the deuterated sample remained stable after exposure to the air as well as during the melting and vitrification processes. Further calorimetric studies revealed the appearance of a peculiar thermal event before the melting of crystalline MLT-d2, which was assigned by the X-ray diffraction to a local negative thermal expansion of the unit cell. Finally, the high-pressure dielectric experiments indicated a few interesting findings, including the variation in the shape of the structural relaxation peak during compression, the difference in the pressure evolution of the glass transition temperature, and the temperature dependence of activation volume for both MLT species. The variations in these parameters manifest a different impact of the compression/densification on the dynamics of hydrogen and deuterium bonds in the native and partially-deuterated MLT, respectively. [ABSTRACT FROM AUTHOR]

In this study, several experimental techniques were applied to probe thermal properties, molecular dynamics, crystallization kinetics and intermolecular interactions in binary mixtures (BMs) composed of flutamide (FL) and various poly(N-vinylpyrrolidone) (PVP) polymers, including a commercial product and, importantly, samples obtained from high-pressure syntheses, which differ in microstructure (defined by the tacticity of the macromolecule) from the commercial PVP. Differential Scanning Calorimetry (DSC) studies revealed a particularly large difference between the glass transition temperature (Tg) of FL+PVPsynth. mixtures with 10 and 30 wt% of the excipient. In the case of the FL+PVPcomm. system, this effect was significantly lower. Such unexpected findings for the former mixtures were strictly connected to the variation of the microstructure of the polymer. Moreover, combined DSC and dielectric measurements showed that the onset of FL crystallization is significantly suppressed in the BM composed of the synthesized polymers. Further non-isothermal DSC investigations carried out on various FL+10 wt% PVP mixtures revealed a slowing down of FL crystallization in all FL-based systems (the best inhibitor of this process was PVP Mn = 190 kg/mol). Our research indicated a significant contribution of the microstructure of the polymer on the physical stability of the pharmaceutical—an issue completely overlooked in the literature. [ABSTRACT FROM AUTHOR]

Broadband Dielectric Spectroscopy was applied to investigate molecular dynamics of two anhydrosaccharides, i.e., 1,6-anhydro-β-D-mannopyranose, anhMAN (hydrogen-bonded system) and 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-glucopyranose, ac-anhGLU (van der Waals material), at different thermodynamic conditions. Moreover, the reported data were compared with those recently published for two other H-bonded systems, i.e., 1,6-anhydro-β-D-glucopyranose (anhGLU) and D-glucose (D-GLU). A direct comparison of the dynamical behavior of the materials with a similar chemical structure but significantly differing by the degrees of freedom, complexity, and intermolecular interactions made it possible to probe the impact of compression on the fragility, Temperature-Pressure Superpositioning and pressure coefficient of the glassy crystal/glass transition temperatures ( d T g c / d p ; d T g / d p ). Moreover, the correlation between d T g c / d p determined experimentally from the high-pressure dielectric data and the Ehrenfest equation has been tested for the plastic crystals (anhGLU and anhMAN) for the first time. Interestingly, a satisfactory agreement was found between both approaches. It is a quite intriguing finding which can be rationalized by the fact that the studied materials are characterized by the low complexity (lower degrees of freedom with respect to the molecular mobility) as well as ordered internal structure. Therefore, one can speculate that in contrast to the ordinary glasses the dynamics of the plastic crystals might be described with the use of a single order parameter. However, to confirm this thesis further, pressure-volume-temperature (PVT) experiments enabling calculations of the Prigogine Defay ratio are required. [ABSTRACT FROM AUTHOR]

In this paper, broadband dielectric spectroscopy was applied to investigate molecular dynamics of 1,2,3,4,6-penta-O-(trimethylsilyl)-D-glucopyranose (S-GLU) at ambient and elevated pressures. Our studies showed that apart from the structural relaxation, one well resolved asymmetric secondary process (initially labeled as β) is observed in the spectra measured at p = 0.1 MPa. Analysis with the use of the coupling model and criterion proposed by Ngai and Capaccioli indicated that the β-process in S-GLU is probably a Johari-Goldstein relaxation of intermolecular origin. Further high pressure experiments demonstrated that there are in fact two secondary processes contributing to the β-relaxation. Therefore, one can postulate that the coupling model is a necessary, but not sufficient criterion to identify the true nature of the given secondary relaxation process. The role of pressure experiments in better understanding of the molecular origin of local mobility seems to be much more important. Interestingly, our research also revealed that the structural relaxation in S-GLU is very sensitive to compression. It was reflected in an extremely high pressure coefficient of the glass transition temperature (dTg/dp = 412 K/GPa). According to the literature data, such a high value of dTg/dp has not been obtained so far for any H-bonded, van der Waals, or polymeric glassformers. [ABSTRACT FROM AUTHOR]

Star-shaped glycopolymers due to the attractive combination of the physicochemical, morphological, self-assembly properties along with biological activity have gained increased attention as innovative agents in novel cancer therapies. Unfortunately, the production of these highly desirable biomaterials remains a challenge in modern macromolecular chemistry. The main reason for that is the low polymerizability of ionic glycomonomers originated from their steric congestion and the occurrence of ionic interactions that generally negatively influence the polymerization progress and hinder controllable reaction pathway. In this work, the new ionic sugar monomer was (co)polymerized for the first time via Activator Generated by Electron Transfer Atom Transfer Radical Polymerization (AGET ATRP) using a three-arm resveratrol-based core to obtain star-like (co)polymers. The obtained products were examined in terms of their physicochemical properties and morphology. Aside from the synthesis of these new glycopolymers, also a thorough description of their thermal properties, ability to self-assembly, the formation of stable superstructures was studied in detail. It was found that examined (co)polymers did not show any heterogeneities and phase separation, while their variation of glass transition temperature (Tg) was strictly related to the change in the number of glycomonomer. Also, the stability and shapes of formed superstructures strictly depend on their composition and topology. Finally, we have shown that synthesized carbohydrate-based polymers revealed high antiproliferative activity against several cancer cell lines (i.e., breast, colon, glioma, and lung cancer). The cytotoxic activity was particularly observed for star-shaped polymers that were systematically enhanced with the growing concentration of amine moieties and molecular weight. The results presented herein suggest that synthesized star-shaped glyco(co)polymers are promising as drug or gene carriers in anticancer therapies or anti-tumor agents, depending on their cytotoxicity. [ABSTRACT FROM AUTHOR]

Abstract: A tunable temperature-responsive nanoparticulate system based on the ionic modifications of hydroxypropyl cellulose (HPC) was obtained. Two derivatives of HPC were successfully obtained and characterized: cationic (modified with trimethylammonium groups) and anionic (modified with styrenesulfonate groups). Due to the polycation-polyanion interactions they spontaneously self-assemble into nanoparticles in water. The size and surface charge of the nanoparticles can be controlled by the polycation/polyanion ratio. The resulting structures are spherical with diameters in the range from 150 to 250nm, as confirmed by AFM, SEM, and DLS measurements. The size of the nanospheres increases in elevated temperatures. A model compound, curcumin, known for its anti-cancer and anti-inflammatory properties, was effectively entrapped inside nanospheres. Its release profile was found to be temperature-dependent. [Copyright &y& Elsevier]

In this paper, we studied for the first time the impact of the molecular weight, M n , and the topology on the molecular dynamics of a series of grafted poly(poly(dimethylsiloxane methacrylate)) (polyPDMSMA). The behavior of grafted (molecular brushes) polyPDMSMA and their three-armed counterparts of tailor-made properties prepared by Atom Transfer Radical Polymerization (ATRP) was monitored by means of broadband dielectric spectroscopy (BDS), differential scanning calorimetry (DSC) and comprehensive rheology analysis. Surprisingly, the dielectric loss spectra of all studied polyPDMSMA exhibit the presence of two dielectric relaxation processes above their glass transition temperature, T g. A comparison of dielectric, calorimetric and mechanical data indicated that the faster and slower relaxation processes identified in loss spectra can be related to the segmental and chain dynamics, respectively. Interestingly, we observed that the "local" segmental dynamics of studied polyPDMSMA, involving the mobility of few repeatable units creating a segment, is almost unaffected by neither the length of polymer chain, number of grafts nor its topology. This is also reflected in a weak molecular weight-dependences of T g of studied polyPDMSMA independently to their topology. On the other hand, the time-scale separation between segmental and the chain modes as well as the amplitude of the latter process increase with growing M n of all examined polyPDMSMA. Additionally, it should be mentioned that the mechanical data collected for samples characterized by high molecular weight (of M n > 280 kg/mol) reveal the emergence of additional process (most likely related to the grafts and/or the star arm relaxation) at the intermediate regime, independently to their topology. Interestingly, this mode was observed to be much slower for the star-shaped macromolecules when compared to the grafted polymers, despite their lower M n. This implies that the observed differences are not a result of different molecular weights, but rather originate from a various molecular mechanism due to the different topology of the studied samples. In this context, one can assume that in the case of high-molecular-weight macromolecules, the backbone architecture has a significant influence on the behavior of polymers, including their molecular dynamics. [Display omitted] • Increase of the glass transition of studied polyPDMSMA with their molecular weight. • Loss spectra of polyPDMSMA exhibit multiple dielectric relaxation processes. • Observed dielectric processes were assigned as the chain and segmental modes. • Presence of grafts/arms relaxation (or entanglement segments) in mechanical data. [ABSTRACT FROM AUTHOR]

In this paper, the molecular dynamics as well as inter- and intramolecular interactions in the homogenous solid dispersions (SDs) of active pharmaceutical ingredient - probucol (PRO) with acetylated glucose (acGLU), acetylated sucrose (acSUC), and sucrose acetoisobutyrate (aibSUC), prepared in 5:1 molar ratio, have been investigated using broadband dielectric (BD) and Fourier transform infrared (FTIR) spectroscopy. Importantly, high pressure dielectric measurements revealed that as for neat PRO, a breakdown of the isochronal structural (α) and JG- β exact superpositioning, due to increasing separation between both processes under compression, can also be detected in its mixtures with acetylated saccharides (acSACCHs). Furthermore, the analysis of temperature dependences of JG- β -relaxation times for PRO and PRO-acSACCH SDs at selected isobaric conditions indicated the increase in the cooperativity of the secondary process (reflected in the value of the activation entropy, Δ S β) at elevated pressure in all systems. The mere addition of the small amount of excipient to neat PRO (p = 0.1 MPa) resulted in a greater value of Δ S β (it was the most noticeable in the case of aibSUC). Further FTIR studies carried out on the pressure densified glasses of PRO, and binary mixtures suggested that the observed changes in the cooperativity of the JG- β -process, as well as the failure of the exact isochronal superpositioning of α - and JG- β relaxation times, are due to varying H-bond pattern in the examined single- and two-component systems at high compression/in the presence of saccharide. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • H-bond strength influences the nature of phase transitions in 1-NH 2 -OH and 1-OH-ADM. • There are three transitions between various plastic crystal (PC) phases in 1-NH 2 -OH. • Only one transition between PC and ordinary crystal phases occurs in 1-OH-ADM. • Compression has a strong impact on phase transitions in both examined compounds. In this paper, several experimental techniques, i.e., differential scanning calorimetry, X-ray diffraction, Fourier transform infrared, Raman, and broadband dielectric spectroscopy were applied to study the nature of the phase transitions in 1-adamantylamine (1-NH 2 -ADM, C 10 H 17 N) and 1-adamantanol (1-OH-ADM, C 10 H 16 O). Calorimetric measurements showed one and three endothermic peaks in thermograms for the latter and the former substance, respectively. Indeed, results of spectroscopic investigations indicated that the observed thermal events in 1-NH 2 -ADM correspond to transitions between various plastic crystal (PC) phases (I, II, III, IV), while the endothermic process in 1-OH-ADM can be assigned to a phase transition between the PC and the ordinary crystal (OC). Especially interesting were the outcomes of dielectric studies carried out both at ambient and high-pressure conditions, during heating and cooling cycles. They showed: i) noticeable changes in the frequency dependencies of the imaginary ( ε ' ' ) and real ( ε ') parts of the complex dielectric permittivity that occurred around temperatures of the characteristic endothermic events detected by the calorimetry, and ii) significant fluctuations of ε ' ' and ε ' at pressures attributed to the respective phase transitions. Moreover, the pressure coefficients of the phase transition temperatures were estimated to be approximately equal to 0.2 K/MPa for both compounds. In turn, volume variation (Δ V) at the PC (II)-PC (III) and PC (III)-PC (IV) transition temperatures for 1-NH 2 -ADM was essentially different than Δ V for the PC-OC transition in 1-OH-ADM. [ABSTRACT FROM AUTHOR]

The main focus of this work was to establish a correlation between surface topography and chemistry and surface colonization by lactic acid bacteria. For this reason, we chose gold substrates with different surface architectures (i.e., smooth and nanorough) that were characterized by atomic force microscopy (AFM), electron scanning microscopy (SEM), and X-ray diffractometry (XRD). Moreover, to enhance biocompatibility, we modified gold substrates with polymeric monolayers, namely cationic dextran derivatives with different molar masses. The presence of those layers was confirmed by AFM, infrared spectroscopy (IR), and X-ray photoelectron spectroscopy (XPS). In order to determine the adhesion abilities of non-modified and modified gold surfaces, we tested three lactic acid bacteria (LAB) strains (i.e., Lactobacillus rhamnosus GG, Lactobacillus acidophilus, and Lactobacillus plantarum 299v). We have shown that surface roughness influences the surface colonization of bacteria, and the most significant impact on the growth was observed for the Lactobacillus rhamnosus GG strain. What is more, covering the gold surface with a molecular polymeric film by using the layer-by-layer (LbL) method allows additional changes in the bacterial growth, independently on the used strain. The well-being of the bacteria cells on tested surfaces was confirmed by using selective staining and fluorescence microscopy. Finally, we have determined the bacterial metabolic activity by measuring the amount of produced lactic acid regarding the growth conditions. The obtained results proved that the adhesion of bacteria to the metallic surface depends on the chemistry and topography of the surface, as well as the specific bacteria strain. [ABSTRACT FROM AUTHOR]

The pharmacokinetic profile and tissue uptake of daidzein (DAI) was determined in rat serum and tissues (lungs, eyes, brain, heart, spleen, fat, liver, kidney, and testes) after intravenous and intraperitoneal administration of DAI in suspension or complexed with ethylenediamine-modified γ-cyclodextrin (GCD-EDA/DAI). The absolute and relative bioavailability of DAI suspended (20 mg/kg i.v. vs. 50 mg/kg i.p.) and complexed (0.54 mg/kg i.v. vs. 1.35 mg/kg i.p.) was determined. After i.p. administration, absorption of DAI complexed with GCD-EDA was more rapid (tmax = 15 min) than that of DAI in suspension (tmax = 45 min) with a ca. 3.6 times higher maximum concentration (Cmax = 615 vs. 173 ng/mL). The i.v. half-life of DAI was longer in GCD-EDA/DAI complex compared with DAI in suspension (t0.5 = 380 min vs. 230 min). The volume of distribution of DAI given i.v. in GCD-EDA/DAI complex was ca. 6 times larger than DAI in suspension (38.6 L/kg vs. 6.2 L/kg). Our data support the concept that the pharmacokinetics of DAI suspended in high doses are nonlinear. Increasing the intravenous dose 34 times resulted in a 5-fold increase in AUC. In turn, increasing the intraperitoneal dose 37 times resulted in a ca. 2-fold increase in AUC. The results of this study suggested that GCD-EDA complex may improve DAI bioavailability after i.p. administration. The absolute bioavailability of DAI in GCD-EDA inclusion complex was ca. 3 times greater (F = 82.4% vs. 28.2%), and the relative bioavailability was ca. 21 times higher than that of DAI in suspension, indicating the need to study DAI bioavailability after administration by routes other than intraperitoneal, e.g., orally, subcutaneously, or intramuscularly. The concentration of DAI released from GCD-EDA/DAI inclusion complex to all the rat tissues studied was higher than after administration of DAI in suspension. The concentration of DAI in brain and lungs was found to be almost 90 and 45 times higher, respectively, when administered in complex compared to the suspended DAI. Given the nonlinear relationship between DAI bioavailability and the dose released from the GCD-EDA complex, complexation of DAI may thus offer an effective approach to improve DAI delivery for treatment purposes, for example in mucopolysaccharidosis (MPS), allowing the reduction of ingested DAI doses. [ABSTRACT FROM AUTHOR]

Different experimental techniques were applied to study thermal and structural properties, strength of H-bonds, possible keto - enol tautomerism and molecular dynamics at various thermodynamic conditions in the H-bonded active substance, curcumin (CRM). Dielectric measurements revealed dynamical features of examined compound that are uncharacteristic for the associated systems. This includes enormously large pressure coefficient of the glass transition temperature and prominent drop of the fragility with compression. Simultaneously, the shape of α -process slightly broadened at elevated pressures. Infrared investigations demonstrated that this effect is related to the variation in the population of H-bonds. Moreover, we studied the changes in the structural and dynamical properties of the glasses prepared upon cooling of the melt (ordinary glass, OG) and the one obtained after compression of CRM in the liquid phase and decompression at T = 293 K (dense glass, DG). Interestingly, during the aging of the latter sample, a clear shift of the β -relaxation towards higher frequencies was noted. This unexpected result indicated that the density of DG is probably getting smaller with time. Complementary X-ray diffraction experiments confirmed this supposition. Additionally, they showed that in DG there are traces of polymorph II of CRM that has a higher density than initial crystals (polymorph I). Finally, infrared studies demonstrated that H-bond pattern in DG is slightly different with respect to OG. Furthermore, Raman investigations suggested that probably keto - enol tautomerism might be shifted towards diketo form in the glass obtained at high compression. Our investigations are very interesting in the context of better understanding of the behavior of associated systems at high compression as well as provide a better insight into dynamics of higher density glasses produced at elevated pressures. Unlabelled Image [ABSTRACT FROM AUTHOR]

We report, for the first time, the metal-free green synthesis of linear poly(vinyl pyrrolidone) (PVP) homopolymers of molecular weight higher than 100 kg mol−1 and narrow dispersities via thermal and photo-induced free radical polymerisation carried out within alumina nanoporous membranes acting as “nanoreactors”. [ABSTRACT FROM AUTHOR]

In this paper, the high-pressure calorimetry was used to monitor the heat of the polymerization of bisphenol-A diglycidyl ether (DGEBA) mixed with a stoichiometric amount of aniline over a wide range of pressure (p = 0.1–350 MPa at T = 298.15 K). To the best of our knowledge, this is the first high-pressure calorimetric study of the reaction kinetics of the epoxy resin curing processes. The collected novel experimental data were analysed with two models: the original Kamal and its modified version taking into account the real monomer conversion, which provides insight into the progress of two subsequent non-catalyzed and catalyzed reactions occurring during the step growth polymerization. It was found that the determined rate constants are sensitive to pressure and model dependent, resulting in different activation volumes, which fall within the range from −16 cm3/mol to −26 cm3/mol. Interestingly, these values are similar to those reported for the epoxide ring-opening polymerization reaction, which changes in the range between −15 cm3/mol to −20 cm3/mol. In addition, the analysis of the high-pressure data revealed that the original Kamal model fails to describe kinetic curves obtained for the polymerization reaction, where the monomer conversion is far below 100%. Interestingly, such effects are considered to be due to the change in the mechanism of the reaction from mass to the diffusion-controlled regime. Here, we explicitly have shown that it has nothing to do with this phenomenon since after considering solely the real monomer conversion in the Kamal model fits, quality has been significantly improved. As a consequence, estimated rate constants are more reliable. Results presented herein clearly indicated that high-pressure experiments provide a new perspective to understand the progress of the classical reactions, as step-growth polymerization that has mainly been studied as a function of the chemical composition and temperature. Image 1 - High-pressure calorimetric data for step-growth polymerization (SGP) are presented - Original Kamal and modified version considering the monomer conversion were tested - Original model fails if the real monomer conversion is far below 100% - Rate constants are sensitive to pressure and model dependent - Activation volumes of catalyzed and non-catalyzed reactions in SGP are different [ABSTRACT FROM AUTHOR]

Highlights • There are marked differences in dynamics of modified linear and cyclic carbohydrates. • A variation in the distribution of τ α between linear and cyclic compounds is observed. • The evolutions of the T g and m versus M w in both groups of materials are different. • The shape of the α -process in saccharides of the same topology doesn't change with M w. Abstract In this paper, the molecular dynamics and thermal properties of representative acetylated linear and cyclic oligosaccharides: acTRE, acRAF, acSTA, ac-α-CD, ac-β-CD, ac-γ-CD, have been investigated by using broadband dielectric spectroscopy and differential scanning calorimetry. We found that there are marked differences in the dynamics of the structural and secondary relaxation processes in both groups of materials. Just to mention a variation in the distribution of the structural relaxation times as well as different evolutions of the glass transition temperature (T g) and fragility (m) versus molecular weight (M w), which seem to be affected by the shape of the molecule, strain in the carbohydrate ring and mobility of side acetyl moieties. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated dielectric response at ambient and elevated pressure of poly(mercaptopropyl)methylsiloxane (PMMS) based oligomeric brushes, where the thiol moiety was substituted by various butyl acrylate isomers (n -butyl acrylate (nBA), iso -butyl acrylate (isoBA), tert -butyl acrylate (tertBA)). It was found that the glass transition temperature, T g , of PMMS is much lower with respect to the other systems despite its ability to form weak hydrogen (H) bonds. What is more, the length scale of cooperativity was the highest in homopolymer and scaled with the steric hindrance of the graft. We also demonstrated that in the examined grafted copolymers, there is one broad relaxation process in dielectric spectra which is wider than that recorded in mechanical response. That probably means that similarly to PMMS, there are two relaxation processes above T g in grafted copolymers. However, due to similar timescale, they cannot be separated. Further, high-pressure experiments revealed that pressure coefficient of the glass transition temperature, d T g / d p , as well as the activation volume, Δ V , calculated for the segmental process surprisingly does not scale with either the size of monomer nor steric hindrance. This unexpected result must be related to the specific structure adopted by the studied grafted oligomers. Presented herein data expand our understanding on the impact of topology on the dynamics of polymers at ambient and high pressure. [Display omitted] • The glass transition temperature is strongly affected by a graft structure. • All grafted materials revealed the broad segmental relaxation process. • The shape of the α -process remains constant with pressure for all materials. • The pressure coefficient of the glass transition changes with graft structures. [ABSTRACT FROM AUTHOR]

The present work aims at development of novel hybrid materials from genipin crosslinked collagen or collagen/chitosan hydrogels containing various types of TiO 2 nanoparticles characterized with different anatase/rutile ratios. Collagen and chitosan were selected as hydrogel components since they are biopolymers being, like collagen, the major compound present in extracellular matrix or exhibit structural similarity to glycosaminoglycans, like chitosan. TiO 2 nanoparticles were introduced to the hydrogel matrices to improve their mechanical properties as well as bioactivity. A series of twelve novel hybrid materials were prepared and their physicochemical, mechanical and biological properties were evaluated. It was found that TiO 2 nanostructures introduced to the hydrogels have significant influence on the swelling properties of the synthesized hybrids and their impact is strongly dependent on the type of matrices. The surfaces of hybrid materials were found to be more hydrophilic than these of corresponding hydrogel matrix. It was also observed that, the storage modulus values of the hybrids based on collagen-chitosan hydrogel are comparable to these for plain hydrogels what indicates that the mechanical properties of the materials obtained are satisfactory for possible biomedical application. The in vitro cell culture studies have shown that prepared materials are biocompatible as they can support mitochondrial activity of MEFs as well as MG-63 cells. In vitro experiments performed under simulated body fluid (SBF) conditions have revealed that all studied TiO 2 nanoparticles present in hydrogel matrices, regardless of anatase/rutile ratio, successfully induced formation of apatite-like structures. The hybrid materials developed here are promising candidates for preparation of bioactive, injectable scaffolds for tissue engineering. [ABSTRACT FROM AUTHOR]

Background: The aim of this study is to assess if the application of different methods of active recovery (working the same or different muscle groups from those which were active during fatiguing exercise) results in significant differences in muscle performance and if the efficiency of the active recovery method is dependent upon the specific sport activity (training loads). Design: A parallel group non-blinded trial with repeated measurements. Methods: Thirteen mountain canoeists and twelve football players participated in this study. Measurements of the bioelectrical activity, torque, work and power of the vastus lateralis oblique, vastus medialis oblique, and rectus femoris muscles were performed during isokinetic tests at a velocity of 90°/s. Results: Active legs recovery in both groups was effective in reducing fatigue from evaluated muscles, where a significant decrease in fatigue index was observed. The muscles peak torque, work and power parameters did not change significantly after both modes of active recovery, but in both groups significant decrease was seen after passive recovery. Conclusions: We suggest that 20 minutes of post-exercise active recovery involving the same muscles that were active during the fatiguing exercise is more effective in fatigue recovery than active exercise using the muscles that were not involved in the exercise. Active arm exercises were less effective in both groups which indicates a lack of a relationship between the different training regimens and the part of the body which is principally used during training. [ABSTRACT FROM AUTHOR]

Development of silicone stabilized liposomes which can serve as novel drug nanocarriers is presented. Silicone precursor 1,3,5,7-tetramethylcyclotetrasiloxane (D 4 H ) was introduced into the bilayer of the cationic liposomes prepared from egg yolk phosphatidylocholine (PC) and double-tailed dimethyldioctadecylammonium bromide (DODAB). The silicone material was created inside of the liposomal bilayer in the base-catalyzed polycondensation process of the D 4 H what was confirmed employing 29 Si solid-state MAS NMR and FTIR measurements. Surfactant lysis experiments revealed that resulted systems can be effectively stabilized. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements demonstrated that the silicone-stabilized liposomes have typical lipid vesicle’s morphology and mean hydrodynamic diameters in the range of about 110 nm. They have considerably lower tendency for aggregation than the pristine liposomes. The permeability of vesicles can be tuned by introducing various amounts of silicone precursor into the liposome bilayer, as confirmed in calcein-release studies. The effect of fetal bovine serum (FBS) on the stability of liposomes was also tested in in vitro studies. Biological studies revealed that resulted liposomes can be considered as possible drug nanocarriers because they are not toxic to human skin fibroblasts (HSFs) and mouse embryonic fibroblasts (MEFs). [ABSTRACT FROM AUTHOR]

[Display omitted] • The unique high-pressure infrared, dielectric, and volumetric data were analyzed. • T and p dependence of H-bonding energy along various isolines was studied. • A phase diagram of 2E1H, identifying isolines in the T - p plane, was constructed. • T controls the intramolecular dynamics of O H units in 2E1H. • The impact of density fluctuation grows with increasing T and weakening of HBs. The nature of H-bonding interactions is still far from being understood despite intense experimental and theoretical studies on this subject carried out by the leading research centers. In this paper, by a combination of unique high-pressure infrared, dielectric and volumetric data, the intramolecular dynamics of hydroxyl moieties (which provides direct information about H-bonds) was studied along various isolines, i.e., isotherms, isobars, isochrones, and isochores, in a simple monohydroxy alcohol (2-ethyl-1-hexanol). This allowed us to discover that the temperature controls the intermolecular hydrogen bonds, which then affect the intramolecular dynamics of O H units. Although the role of density fluctuations gets stronger as temperature rises. We also demonstrated a clear connection between the intra- and intermolecular dynamics of the associating liquid at high pressure. The data reported herein open a new perspective to explore this important aspect of the glass transition phenomenon and understand H-bonding interactions at varying thermodynamic conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] Modified oligosaccharides with cyclic topology seem to be promising excipients for the preparation of Amorphous Solid Dispersions (ASDs), especially with those Active Pharmaceutical Ingredients (APIs), which have a strong crystallization tendency from the amorphous/glassy state. Herein, the usefulness of two acetylated cyclodextrins (ac-α-CD and ac-β-CD) with various molecular weights (M w) as stabilizers for the supercooled metronidazole (Met) has been discussed. X-ray diffraction (XRD) studies carried out on Met-acCDs mixtures (prepared in molar ratios from 1:2 to 5:1) showed that the system with ac-α-CD containing the highest amount of API (5:1 m/m) crystallizes immediately after preparation, whereas all Met-ac-β-CD ASDs remain stable. What is more, long-term XRD measurements confirmed that the Met-ac-α-CD 2:1 m/m system crystallizes after 100 days of storage in contrast to the same system containing ac-β-CD. The non-isothermal calorimetric data revealed that the activation barrier for crystallization (E c r) in ASDs with the oligosaccharide having a greater M w (i.e., composed of seven acGLU molecules) is slightly higher. Finally, to explain the differences in behavior between the mixtures with both acCDs, infrared studies, DFT calculations and Molecular Dynamics simulations were performed. All methods excluded the scenario of API incorporation inside the acCDs' core. On the other hand, obtained results suggested that in comparison to ac-α-CD, the greater amount of Met molecules might be bounded on the outside surface of ac-β-CD. Therefore, this modified saccharide is a better stabilizer of the examined API. [ABSTRACT FROM AUTHOR]

This work demonstrates the effect of a high dc bias field (up to 160 kV/cm) on the polyaddition reaction of the modeled epoxy resin system. Polymerization of bisphenol A diglycidyl ether (DGEBA) supported by high electric field results in obtaining epoxides with significantly increased molecular weight, which is seven-fold higher than the zero-field reference (M n = 4.7 kg/mol). We also found a markedly reduced dispersity (Ð = 1.52 at 0 kV/cm, Đ = 1.21 at 160 kV/cm). The molecular weight and dispersity of obtained polymers change almost linearly with the reaction time. By following polymerization kinetics in the real-time of the experiment, via dielectric spectroscopy, we observe slowing down the reaction progress at dc fields of E = 160 kV/cm, compared to the zero-field case, E = 0 kV/cm. The polymer materials obtained in the presence/absence of static electric fields exhibit distinctly different glass transition temperatures. Our study highlights a better control over the reaction and product properties attained by using only the magnitude of the applied field as the control variable. Thus, a high electric field could provide an alternative pathway in synthesizing and developing advanced polymer materials using simpler, "green", less-expensive, and technologically demanding approaches. [Display omitted] [ABSTRACT FROM AUTHOR]

The crystallization and melting behavior of phenyl salicylate under confinement were studied by means of dielectric spectroscopy (BDS) and differential scanning calorimetry (DSC). From the analysis of the kinetics of crystallization we established that crystals formed in bulk and under confinement are characterized by varying the rate of growth, dimensionality, and crystal lattice. It was shown that depending on the degree of confinement the crystallization can be accelerated or suppressed completely. Interestingly, we also found that the activation barrier for the crystallization either increases or decreases with respect to the bulk conditions. Further investigation of the melting temperature of the formed crystals indicated unequivocally that it is connected to the formation of different polymorphic forms of salol. Additional FTIR measurements confirmed that thesis. Based on calorimetric data obtained for the confined samples, we concluded that at pores of higher diameter the unstable (monoclinic) form is preferred, while at lower pores the original stable (orthorhombic) crystal is formed. [ABSTRACT FROM AUTHOR]

A new method for fabrication of chitosan-based hydrogel implants intended for peripheral nervous tissue regeneration was developed. The method is based on an electrodeposition phenomenon from a solution of chitosan and organic acid. In order to increase the mechanical strength of the implant, the solution was enriched with hydroxyapatite. Hydroxyapatite served as a source of calcium ions too. The influence of the concentration of the polymer and the additive on chemical, mechanical as well as biological properties of the obtained implant was evaluated. The study showed great dependence of the initial solution composition mainly on the physicochemical properties of the resulting structure. Basic in vitro cytotoxic and pro-inflammatory assays showed biocompatibility of manufactured implants, therefore, animal experimentations may be considered. [ABSTRACT FROM AUTHOR]

In this paper, 1,6-anhydro-β-D-glucopyranose (anhGLU), 1,6-anhydro-β-D-mannopyranose (anhMAN), and 1,6-anhydro-β-D-galactopyranose (anhGAL), three new materials that form the Orientationally Disordered Crystal (ODIC) phase, have been thoroughly investigated using various experimental techniques. All measurements clearly indicated that these compounds possess a series of very interesting physical properties that are considerably different than those reported for ordinary plastic crystals. X-Ray diffraction investigations have revealed enormously long-range static correlations between molecules, reaching even 120 Å. Moreover, dielectric studies showed that besides Freon 113, the investigated anhydrosaccharides are the most fragile systems that form the ODIC phase. Further analysis of Fourier transform infrared spectra indicated that such peculiar behavior of anhydrosaccharides might be closely related to multidirectional H-bonds of various strengths that most likely affect the number of available conformations, density states, and the potential barriers in the energy landscape of these compounds. This is consistent with the results from previous reports [L. C. Pardo, J. Chem. Phys. 124, 124911 (2006) and Th. Bauer et al., J Chem. Phys. 133, 144509 (2010)] showing that the higher fragility of Freon 112 as well as a mixture of 60% succinonitrile and 40% glutaronitrile (60SN-40GN) can be closely related to the enhanced conformational ability and additional disorder introduced by various substituents, which further make energy landscape more complex. Finally, by studying the properties of 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-glucopyranose (ac-anhGLU) it was found that besides the shape of the molecules, H-bonds or generally strong intermolecular interactions are extremely important parameters contributing to the ability to form the plastic phase. This is in line with current observations that in most cases the ODIC phase is created in highly interacting compounds. [ABSTRACT FROM AUTHOR]